A magnesiothermic route to multicomponent nanocomposites of FeSi2@Si@graphene and FeSi2@Si with promising anode performance

Abstract The multicomponent nanocomposites of FeSi 2 @Si@graphene and FeSi 2 @Si are synthesized via the magnesiothermic reduction of core-shell Fe 3 O 4 @SiO 2 nanoparticles with/without graphene oxide shell. In the course of the magnesiothermic reaction, the SiO 2 and Fe 3 O 4 components in the Fe 3 O 4 @SiO 2 core-shell particles are transformed into elemental Si and FeSi 2 , respectively. The formation of intimately-coupled composite structure consisting of Si and FeSi 2 domains as well as the coating of graphene layer is verified by high resolution-transmission electron microscopy. Both the nanocomposites of FeSi 2 @Si@graphene and FeSi 2 @Si show promising anode performance for lithium ion batteries, indicating a beneficial role of the electrochemically inactive FeSi 2 domains in alleviating the drastic expansion/contraction of elemental Si during the electrochemical cycling. The better cyclability and rate characteristic are obtained for the FeSi 2 @Si@graphene nanocomposite than for the graphene-free FeSi 2 @Si one, which is attributable to the depression of pulverization and the enhancement of electrical conductivity upon the coating of graphene layer. The present work highlights that the magnesiothermic reaction provides a powerful synthetic route to multicomponent Si-based nanocomposites with tailored composition and complex geometry.